The purpose of this investigation is to examine the hypothesis that fat content within skeletal muscle as determined by computed tomography, magnetic resonance imaging techniques is increased in obesity and that this parameter is strongly related to insulin resistance and diabetes. We will use the glucose clamp technique and in diabetic subjects, stable isotope tracer (deuterium-labeled glucose) infusions to measure insulin sensitivity. In addition, we will analyze muscle biopsy samples for lipid content within skeletal muscle for fiber type.